1. Field of the Invention
The present invention relates to a system microscope that is capable of simultaneously observing a specimen in upward and downward directions.
2. Description of the Related Art
There is known a system microscope that includes, as a basic configuration, an inverted microscope, which observes a specimen from its lower side, and also includes the configuration of a microscope with upright frame by disposing observation means on the upper side of the specimen.
An example of the system microscope that is based on this concept is disclosed in the drawings of Jpn. Pat. Appln. KOKAI Publication No. 2000-89124. As is shown in FIG. 1, this system microscope is capable of simultaneously observing the same part of a specimen in upward and downward directions by commonly combining the optical axis of the microscope with upright frame and that of the inverted microscope. In FIG. 1, light from an illumination light source 102 passes through an excitation filter 104 and is reflected by a dichroic mirror 106. The reflected light illuminates the upper side of a specimen 101 via an objective lens 110. Light (fluorescent light) from the specimen 101 is converted to parallel light via the objective lens 110. The parallel light passes through the dichroic mirror 106, and is reflected by a reflection mirror 114 via an emission filter 108 and a tube lens 112. The reflected light is visually observed by an eyepiece 116.
Light from an illumination light source 103 passes through an excitation filter 105 and is then reflected by a dichroic mirror 107. The reflected light illuminates the lower side of the specimen 101 via an objective lens 111. Light (fluorescent light) emitted from the specimen 101 is converted to parallel light via the objective lens 111. The parallel light passes through the dichroic mirror 107, and is reflected by a reflection mirror 115 via an emission filter 109 and a tube lens 113. The reflected light is visually observed by an eyepiece 117.
In this system microscope, depending on purposes of use, the filter may be removed, or the dichroic mirror may be replaced with a 45° incidence filter or a beam splitter (half-mirror). Thereby, for example, the focal positions of the objective lenses 110 and 111, which are disposed on the upper and lower sides of the specimen 101, can independently be set relative to the specimen 101. This enables simultaneous observation of parts of the specimen 101 having a thickness, which are located at different levels of the specimen 101. In addition, by shifting the excitation filter 104 off the optical axis, it becomes possible to perform transmissive observation in which the specimen 101 is illuminated from above and observed from below, and fluorescent observation in which the specimen 101 is illuminated from below and observed from above. Thereby, the fluorescent observation and transmissive observation of the same part of the specimen 101 can be performed at the same time without lowering the fluorescent contrast.
In the system microscope disclosed in KOKAI 2000-89124, however, the relative position between a lower optical path P1, which is constituted by the objective lens 111 and tube lens 113 that are disposed below the specimen 101, and an upper optical path P2, which is constituted by the objective lens 110 and tube lens 113 that are disposed below the specimen 101, are fixed and invariable. Consequently, only a part at the same position of the specimen 101 can be observed at the same time. In other words, different positions on the specimen 101 in a plane perpendicular to the optical axis P cannot be observed at the same time by the upper and lower objective lenses 110 and 111.
To solve this problem, there is known a system microscope, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-55282, which includes a driving mechanism capable of moving the upper-side objective lens in a plane perpendicular to the upper-side observation optical path. Specifically, in the system microscope of KOKAI 2002-55282, the upper-side objective lens is movable relative to the upper-side observation optical path. By moving the upper-side objective lens, the relative position between the lower-side objective lens and upper-side objective lens is varied so that different positions on the specimen in a direction perpendicular to the optical axis can be observed at the same time by the upper and lower objective lenses. For example, in a case where a laser oscillator is used as the upper-side illumination light source and a laser beam is radiated on the specimen via the upper optical path, the upper-side objective lens may be moved in the plane perpendicular to the upper-side optical path, thus being able to move the radiation position of the laser beam on the specimen. The same advantageous effect is also obtainable in a case where a laser oscillator is used as the lower-side illumination light source and a laser beam is radiated on the specimen via the lower-side optical path.
However, with the system microscope of KOKAI 2002-55282, the following problem is encountered. FIG. 2 shows a state in which different locations on a specimen 120 in a plane perpendicular to an optical axis P are observed at the same time by upper and lower objective lenses 121 and 122. FIG. 3 shows a state in which illumination light is radiated by the upper and lower objective lenses 121 and 122 at the same time on two different locations in a plane perpendicular to the optical axis P.
In the case where different positions in the plane perpendicular to the optical axis P of the specimen 120 are observed by the upper and lower objective lenses 121 and 122, as shown in FIG. 2, only the upper objective lens 121 is moved in the plane perpendicular to the upper-side optical path P2. In this case, the positional relationship between the upper objective lens 121 and upper tube lens 123 is displaced, and part of the parallel light from the upper objective lens 121 may not enter the upper tube lens 123. If the image of the specimen 120 is observed from above in this state, such a problem would arise that an eclipse of the observed image (indicated by hatching in FIG. 2) occurs.
Besides, as shown in FIG. 3, in the case where illumination light is radiated via the upper and lower objective lenses 121 and 122 at the same time on two different positions in the plane perpendicular to the optical axis P, the upper objective lens 121 is moved in the plane perpendicular to the upper-side optical path P2. The illumination light, which is to be radiated on the specimen 120 from above at this time, is reflected by the dichroic mirror 124 that is disposed between the upper objective lens 121 and the upper tube lens 123, and the reflected light is guided to the upper-side optical path P2. Thus, if the positional relationship between the dichroic mirror 124 and upper-side objective lens 121 is displaced, as shown in FIG. 3, part of the beam (indicated by hatching) that is reflected by the dichroic mirror 124 may not enter the upper objective lens 121. As a result, such a problem arises that illumination light that is radiated from the upper objective lens 121 on the specimen 120 become non-uniform.
Similarly, in a case where a laser beam is used as the illumination light source and the laser beam is radiated on the specimen 120 as illumination light, part of the laser beam that is reflected by the dichroic mirror 120 may not enter the upper objective lens 121. Consequently, such a problem arises that the shape of the laser spot deforms and the laser intensity distribution in the laser spot becomes non-uniform.